Embodiments of the current invention are related to solar cells and solar panels. More specifically, embodiments of the current invention relate to a thin film solar collector and method.
In the past few decades more and more effort has been directed to develop solar panels, using photovoltaic (PV) devices, which can optimize and maximize energy collection from existing available surfaces, whether they are stationary or mobile. Examples of available surfaces are, inter alia: vehicle or aircraft external surfaces and facets of building structures (otherwise known as building-integrated PV).
The harvesting potential of PV devices is determined by two main attributes:                conversion efficiency—expressed as the portion of the incident/incoming light converted into electric current; and        optical acceptance—the ability of the device to capture incoming light without the incoming light being reflected or scattered from the surface of the device.        
In general, the two attributes noted hereinabove determine the generation or harvesting potential for a defined group of devices. Generally, the conversion efficiency of photovoltaic semiconductor devices varies from material to material. Currently there are 3 dominant types of PV cells:                Thin films—having lower conversion efficiencies but high optical acceptance        Crystalline Silicon—most commonly used, having moderate efficiency and moderate optical acceptance; and        Multi junction concentrator cells—having the highest efficiency, low optical acceptance, and usually utilizing concentrating optics. Due to their low optical acceptance, multi junction concentrator cells utilize the direct component of incident solar irradiation, Direct Normal Irradiance (DNI), as known in the art. Solar tracking mechanisms are used to maintain alignment of the cell with incident DNI. These concentrator cells are conventionally referred to as “concentrated photovoltaics” (CPV).        
Prior art, applications, and companies producing thin films for PV applications include:                Flexible “Power Plastic”, as noted in the Konkara Brochure, and other brochures available at http://www.konarka.com/index.php/company/tech-sheets-and-brochures/, whose disclosure is incorporated herein by reference, by Konarka Technologies, Inc., 116 John Street, Lowell, Mass. 01852, USA;        Thin film applications by AltaDevices Inc, 545 Oakmead Parkway, Sunnyvale, Calif. 94085, USA, as described on http://www.altadevices.com/technology-overview.php;        U.S. Pat. No. 7,846,759 to Atwater et al., entitled “Multi-junction solar cells and methods of making same using layer transfer and bonding techniques”, whose disclosure is incorporated herein by reference;        Integrated wide angle light collection solar cells, as described in PV-Magazine, October 2012, whose disclosure is incorporated herein by reference, produced by Solar3D, Inc., 6500, Hollister Ave. Suite 130, Santa Barbara, Calif. 93117, USA.        
Kurtz, in a publication entitled: “CPV 101: Intro to CPV Technology: Opportunities and Challenges”, NREL/PR-520-46924, 26 Oct. 2009, whose disclosure is incorporated herein by reference, discusses a number of developments related to CPV. Reference is presently made to FIG. 1, prior art—from Kurtz, above, which is a timeline graph showing the development of solar cells over time versus their respective energy conversion efficiencies. It can be seen that from the 1990's through today, multi junction CPV cells appear to have the highest energy efficiencies compared to alternate technologies.
For terrestrial applications, high solar irradiation levels are achieved by light being concentrated onto CPV cells using optics assemblies (also referred herein below in the specification and claims as “optics”). Currently-available MJ cells with optics assemblies operate optimally at irradiation concentration levels of 500-1,000 suns, where a “sun” is defined as 1,000 W\m2. Such optic assemblies have two characteristics:                a. Focal length considerations, yielding CPV panels/modules having significant depth (the focal length being commonly approximately equal to the diagonal of the collective primary lens or mirror);        b. Tracking systems and/or mechanisms—to maintain optimal optical collection of the entire system, system optics, and panels substantially normal to the sun. Dual and single axis tracking mechanisms, as known in the art, are used to achieve this.        
Both of the characteristics noted hereinabove significantly increase the cost and complexity of CPV solutions. There is therefore a need for CPV assemblies having a low depth panel/thin profile while exhibiting high conversion efficiency and a reduction/elimination of complicated and costly tracking systems.